A tablet PC, or pen computer, is a notebook or slate-shaped mobile computer, equipped with a touch screen or graphics tablet/screen hybrid technology that allows the user to operate the computer with a stylus, digital pen, or fingertip instead of a keyboard or mouse. Tablet PCs offer a more natural form of input, as sketching and handwriting are a much more familiar form of input than a keyboard and mouse, especially for people who are new to computers. Tablet PCs can also be more accessible because those who are physically unable to type can utilize the additional features of a tablet PC to be able to interact with the electronic world. Other devices also offer similar touch input capabilities, such as touch screen mobile phones.
Multi-touch (or multi-touch) denotes a set of interaction techniques that allow computer users to control graphical applications using multiple fingers or input devices (e.g., a stylus). Multi-touch implementations usually include touch hardware (e.g., a screen, table, wall, and so on) and software that recognizes multiple contemporaneous touch points. Multi-touch stands in contrast to traditional touch screens (e.g., computer touchpad, ATM, shopping kiosk) that only recognize one touch point at a time. Multi-touch hardware can sense touches using heat, finger pressure, high capture rate cameras, infrared light, optic capture, tuned electromagnetic induction, ultrasonic receivers, transducer microphones, laser rangefinders, shadow capture, and other mechanisms. Many applications for multi-touch interfaces exist and application designers and users are proposing even more. As a new input method, multi-touch offers the potential for new user experience paradigms.
An application cannot use multi-touch hardware without an interface for the application software to receive information from the multi-touch hardware. Although newer operating systems, such as Microsoft Windows 7, provide an abstraction layer to receive uniform multi-touch data from many different types of multi-touch hardware, this data is not easily accessible from a web browser and other sandboxed environments. Web browsers often provide isolated or sandboxed environments that strictly control what software (sometimes called a plug-in or control) is allowed to execute on a client computer system. Users have an expectation that using a web browser or other sandbox is a safe experience that will not cause data corruption or other negative impact to their computer system. Newer web applications may make use of feature-rich web plug-ins like Microsoft Silverlight to build rich applications that are nearly or more functional than their desktop counterparts. Unfortunately, sandboxed environments and applications running within them have thus far had difficulty receiving and acting on multi-touch input. This produces a very limited potential market for sandbox application authors and reduces the incentive to write applications supporting multi-touch interactions.